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Practitioners are gaining a wider understanding of the medications indicated for osteoarthritis management and are learning to decrease the adverse effects of the more potent corticosteroids.
Along with steroids, a variety of modern systemic products is available to address joint therapy—both intra-articular (Hyvisc, Hyalovet, Hylartin V, Adequan) and intravenous (Legend) hyaluronic acid, and intramuscular polysulfated glycosaminoglycans, or PSGAGs (Adequan).
Although these medications aren’t new, Dean Hendrickson, DVM, MS, associate professor of surgery and chief of Equine Clinical Services at Colorado State University College of Veterinary Medicine, said the challenge is recognizing that not all situations are the same. He said practitioners have to learn to tailor the products’ use to each horse’s needs.
“It’s difficult to answer the question of whether you should use any of these three in combination or individually,” Dr. Hendrickson said. “Many times this is a personal preference. Everyone has a different experience with what he or she has used and what’s been useful. We are just trying to get wiser in how and when we use these products.”
Hyaluronic Acid, PSGAGs
Although treatment protocols for equine osteoarthritis are often a veterinarian’s personal choice, there are general rules of thumb.
“We will typically use the hyaluronic acid when there is minimal to no cartilage change,” Hendrickson said. “We’ll choose PSGAGs when there is inflammation and mild articular cartilage damage, and we will use the corticosteroids when we need a little more potent anti-inflammatory.”
In moderate to advanced cases of osteoarthritis, Nancy Loving, DVM, of Loving Equine Clinic in Boulder, Colo., said the most powerful strategy to control inflammation remains intra-articular therapy, using corticosteroids with or without hyaluronic acid or PSGAGs.
“Following IA therapy, the systemic intravenous and intramuscular medications are useful as adjunct therapy to maintain optimal joint function, and to decrease the frequency and to prolong the spacing intervals between IA treatments,” Dr. Loving said.
Intravenous hyaluronic acid or IM polysulfated glycosaminoglycans can be used successfully at any stage of osteoarthritis, and in fact, practitioners and horse owners will maximize benefits of these drugs that are not specifically promoted, Loving said.
Hendrickson said IM Adequan is often used as a preventive.
“Owners will give it once a month after the initial series in order to provide a maintenance benefit to the animals,” he said.
Gary White, DVM, chief scientific spokesman for Luitpold Equine, agreed.
“The use of IM Adequan as a maintenance drug is especially beneficial, especially in the high-motion, high-load joints like the shoulders, stifles and knees,” Dr. White said.
“Benefits include improved synovial fluid environment through increasing HA production and decreased synovial inflammation.”
“Legend is labeled as a treatment for joint dysfunction related to synovitis associated with osteoarthritis, and there is no claim for Legend to prevent joint disease,” said Kenton Morgan, DVM Dipl. ACT, spokesman for Bayer Veterinary Services, makers of Legend, in Raymore, Mo. “So we cannot market or promote the drug for this use.
“However, in the hands of the veterinarian a great deal of Legend is used in high-level performance disciplines for that very reason. The horses are sound, but Legend is given to help keep them in top form and as insurance to prevent the horse from missing a major competition or event,” Dr. Morgan said.
In this scenario, veterinarians will give Legend IV from once every four weeks, once per week or 48 hours before any major event, or any combination depending on the case.
Adequan is often used the same way, White said.
“Some veterinarians prefer one, some use the other, and some alternate between the two,” White said.
Tips for Osteoarthritis Management
Use the appropriate drug for the right stage of the disease.
If you’re not seeing a response after your full series of hyaluronic acid or polysulfated glycosaminoglycans, or after one injection of steroid, move on to another treatment, said Dean Hendrickson, DVM, MS, associate professor of surgery and chief of Equine Clinical Services at Colorado State University College of Veterinary Medicine.
If you're going to inject steroids, try to give the animal a week to 10 days off from forced exercise.
My clinical perspective is that the steroids last longer,” Dr. Hendrickson said. “We find that the animal needs fewer injections with this lengthy rest. I’m not sure why, but it is my impression that horses that get injected and work hard within three days don't seem to last as long with the steroid effect as those with the longer rest.
Encourage clients to identify and report a problem at its most subtle stages so therapy can arrest the degenerative process as quickly as possible.
Whenever clients have tried to go months past these indications of discomfort, they have mentioned to me that they regretted waiting, said Nancy Loving, DVM, of Loving Equine Clinic in Boulder, Colo.
Steroids are still the most potent anti-inflammatory drug.
“I tell owners of horses with advanced arthritis that using something like Legend or Adequan is like taking a squirt gun to a fire,” Hendrickson said. “You put out a little bit of the flame but if we want to put out the fire we need to bring in the tanker trucks, which are the steroids.”
Research has shown that higher doses of steroids can soften the articular cartilage, which leads to erosion and arthritis in the joint. Yet some of the work conducted at the Orthopedic Research Center at Colorado State University shows that triamcinolone is actually protective of the cartilage.
“We used to lump all steroids in the same group, but as we’ve had a chance to do more work with them, we’ve found that some have great benefit without the detriment,” Hendrickson said.
Triamcinolone is thought to have chrondroprotective properties, which improve joint nutrition and synovial fluid viscosity. This drug is water-soluble so it leaves no deleterious deposits within the joint, yet it retains anti-inflammatory effects for many months, Loving said.
“For the large-range motion joints such as the coffin joints, fetlock joints or carpal joints, the best success is achieved when corticosteroids are combined with hyaluronic acid,” Loving said. “Not all joints require a combination of corticosteroids with hyaluronic acid for best results. The distal hock joints do well as long as an appropriate corticosteroid is injected.
“Some claim to notice better improvement in hock osteoarthropathy when hyaluronic acid is also included, while others don’t think it matters in the distal hock joints.”
“In high-motion joints we recommend triamcinalone and for the low-motion joints we recommend Depo Medral,” [Dean Hendrickson, DVM, MS, associate professor of surgery and chief of Equine Clinical Services at Colorado State University College of Veterinary Medicine] said.
The cost of both steroids are almost identical, Hendrickson and Loving noted; veterinarians just need to carry two different steroids instead of one.
Although none of the drugs mentioned here are pain relievers, by reducing inflammation the source of discomfort is eliminated.
“There is another advantage of using HA products, such as Legend, or PSGAGs, such as Adequan, because you won’t cover up or mask a serious problem in an athlete that could pose a potential risk if the animal continues to compete,” Morgan said.
“There is no question that we are seeing results with these products, particularly if we’re using the medications the way they are supposed to be used,” Hendrickson said.
“If you have a horse with a mild synovitis and it is receiving IV Legend, then you will see a real difference,” he said. “And even more if you use a higher molecular weight hyaluronic acid, like Hyvisc, right in the joint.”
“I have had excellent success using intra-articular therapy with corticosteroids and hyaluronic acid, and in using IV Legend and IM Adequan staggered on a monthly basis to continue joint support,” Loving said.
“There is a notable difference and deterioration in a horse’s performance when a client decreases use or frequency of these medications,” she said.
“Early intervention yields the best results, but clients should also be aware that in spite of favorable results for years, there will come a day when these joint therapies will no longer be able to maintain a horse at the desired skill level of work.”
Sharon Biggs, a frequent contributor to Veterinary Practice News, lives in England.
This article first appeared in the September 2004 issue of Veterinary Practice News.
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